Many mammalian veins are known to have semilunar venous valves located within their lumens for preventing back flow of blood therethrough. In human beings, venous valves are most numerous in the large veins (i.e., those greater than 1/12 in. in diameter) of the extremities, especially of the lower extremities.
In a number of reconstructive vascular surgical procedures, segments of vein are utilized as grafts for replacing or bypassing occluded segments of artery.
For example, in coronary artery bypass graft (CABG) procedures, a segment of saphenous vein may be removed from the patient's leg, prepared for use as a graft, and anastimosted to an occluded coronary artery so as to form a bypass conduit around the coronary artery occlusion. In these saphenous vein CABG procedures, it is typical for the surgeon to prepare the harvested segment of vein for use as a graft by a) inserting an instrument known as a "valvulotome" into the lumen of the vein segment and using such instrument to disrupt the venous valves located therein and also b) reversing the directional orientation of the harvested segment of vein (i.e., turn it end for end) prior to implantation. The disruption of the venous valves and reversal of the directional orientation of the vein segment avoids any potential for any venous valves to remain competent within the harvested graft segment or to interfere with subsequent blood flow through the graft.
Similarly, in in situ vein bypass procedures, a segment of saphenous vein is utilized to bypass one or more blockages in the artery(s) of the leg. In such in situ bypass procedures, the saphenous vein is initially exposed and transected at sites above and below the arterial blockage. Thereafter, a valvulotome device is passed through the lumen of the transected segment of vein and utilized to disrupt all venous valves located therewithin. Thereafter, all side branches or tributaries of the vein segment are ligated or blocked, thereby rendering the vein segment usable as a bypass conduit for the arterial circulation. After the vein segment has been prepared in this manner, the transected ends of the vein segment are anastomosed to the occluded artery, at sites above and below the blockage. In this regard, the prepared vein segment forms an in situ bypass conduit around the arterial blockage.
In both CABG and in situ vein bypass procedures, it is important to make certain that all venous valves located within the vein segment to be utilized as the bypass graft, have been lysed or otherwise rendered incompetent. Numerous venous valve cutting devices or "valvulotomes" have heretofore been utilized for this purpose.
Examples of previously known valvulotome devices, vein stripping apparatus, and other related devices/methods are described in U.S. Pat. Nos. 5,284,478 (Nobles et al), 5,282,813 (Redha), 5,234,450 (Segalowitz), 5,224,949 (Gomringer et al.), 5,192,268 (Shiber), 5,141,491 (Bowald), 5,092,872 (Segalowitz), 5,087,264 (Miller et al.), 5,133,725 (Quadri), 5,152,771 (Sabbaghian et al.), 5,092,872 (Segalowitz), 5,087,265 (Summers), 5,049,154 (Quadri), 5,026,383 (Nobles), 4,952,215 (Ouriel et al.), 4,898,575 (Fischell et al.), 4,768,508 (Chin et al.), 4,729,374 (Alfranca), 4,544,217 (Reed), 4,493,321 (Leather), 3,837,345 (Matar), 2,676,595 (Dyekjaer), 5,171,316 (Mehigan), and in foreign patents/patent publications Nos. FR 2649-309-A (Formichi), 2,044,103A (Ross et al.), FR 002679437 A (Valici), DE 4020-155-A (Storz), PCT WO 93/20764 (Goldberg et al.), WO 92/08414 (Berkshire Inc.), WO 91/01689 (Segalowitz), WO 90/02523 (Bestimmungsstaaten), WO 89/09029 (Taheri), WO 89/06936 (Bowald), WO 88/00458 (Fischell), and 0 248 761 A1 (Fogarty).
In any valvulotome device, it is desirable for the cutting surface(s) of the device to be configured and designed to effectively cut the cusps of the venous valve at sufficient depth to render the valve fully incompetent without causing damage or trauma to the wall intimal surface of the vein. Failure to cut the valve cusps deeply enough may allow remnants of the valve cusps to continue to obstruct flow through the lumen of the vein segment. 0n the other hand, passage of the cutting surface(s) of the device into the luminal wall of the vein may result in frank perforation of the vein, or may otherwise render the vein segment unusable for use as a graft.
In view of the above-explained considerations, there remains a need in the art for the development of improved valvulotome devices which are capable of causing reproducible and consistent lysis of venous valves, while minimizing any potential for traumatization of the wall or intimal layer of the vein in which they are deployed.